Latest Permian chars may derive from wildfires, not coal combustion
Geological Society of America
This is the author accepted manuscript. The final version is available from Geological Society of America via http://dx.doi.org/10.1130/G35920.1.
The Permian-Triassic boundary extinction event was the largest biological crisis of the Phanerozoic. One of the principle triggers for the mass extinction is thought to be greenhouse warming resulting from the release of CH4 from basalt-coal interaction during the extensive Siberian Traps (Russia) eruptions. Observations of organic matter interpreted to be coal combustion products (fly ash) in latest Permian marine sediments have been used to support this hypothesis. However, this interpretation is dependent upon vesicular chars being fly ash (coal combustion derived) and not formed by alternative mechanisms. Here we present reflectance microscopy images of vesicular chars from Russian Permian coals, and chars from modern tundra, peatland, and boreal forest fires, to demonstrate that despite a difference in precursor fuels, wildfires are capable of generating vesicular chars that are morphologically comparable to end-Permian fly ash. These observations, coupled with extensive global evidence of wildfires during this time interval, call into question the contribution of coal combustion to the end- Permian extinction event.
We acknowledge funding from the Natural Environment Research Council and CASE Studentship grant NE/F013698/1 (Hudspith’s Ph.D. thesis, Royal Holloway University of London), for the late Permian coal samples from the Kuznetsk Basin, Siberia, Russia. National Science Foundation (NSF) grant ARC-0612366 (to F.S. Hu) funded the analysis of the boreal and tundra samples, and European Research Council Starter Grant ERC-2013-StG-335891-ECOFLAM funded Hudspith and Belcher for analysis of the modern peatland samples. We thank M.E. Collinson and A.C. Scott for use of reflectance microscope facilities at Royal Holloway University of London, and N. Holloway and S. Pendray for polished block preparation. We also thank four anonymous reviewers for their helpful comments.
Vol. 42, No. 10, pp. 879 - 882